Saturday, November 10, 2018

The anaesthetic drug Ketamine has been shown to be beneficial in some cases of depression and suicidal ideation which have typically failed to respond to other standard antidepressant medications. A new study has explored the actual workings of ketamine in depression and found that the drug can act on the same receptors as opioid pain relievers.

For this the researchers from the Stanford’s Neurosciences Institute included 12 volunteers at first. These cases were all of treatment-resistant depression.

The participants were all given infusion of Ketamine. In addition some were administered naltrexone and others normal saline infusion. Naltrexone is a drug that can block the effects of opioids.

Results showed that those on ketamine and saline combination found relief from their depressive symptoms quickly compared to those on ketamine and naltrexone combination. In fact those on ketamine and saline placebo reported at least a 90 percent reduction in their symptoms within the first three days of the infusion.

No such improvement was seen among those on ketamine and naltrexone. This proved that when the opioid actions are blocked, the ketamine cannot function as an antidepressant. Both groups faced certain side effects of ketamine such as an “out-of-the-body” experience, dysphoric feelings, tripping etc. This also showed that the antidepressant action of Ketamine was separate from its usual actions, which were seen in all participants in either group.

The initial trial plan was to include 30 patients. Due to the dramatic improvement seen in one group and no changes in the other, the team decided to stop the trial prematurely. This was to spare patients useless treatment.

Ketamine has been in news recently due to its unexplored potential as an antidepressant. If proven, researchers believe, this could impact depression research significantly. Ketamine has gathered interest mainly because it does not change the brain chemistry unlike other antidepressants. Co-author Boris Heifets, a clinical assistant professor of anesthesiology, perioperative and pain medicine at Stanford explained that ketamine blocks the brain’s receptors for glutamate. Glutamate is an important neurotransmitter in the brain. Many researchers have thought that glutamate could be the key zone where ketamine acts as an antidepressant. Heifets added that ketamine is not a simple drug and has varied targets which could be responsible for its antidepressant activities. A lot of money has been spent on developing agents that could work on the glutamate receptors and try to mimic ketamine’s antidepressant actions.

This study shows that the approach is incorrect and glutamates are not the target lead author Nolan Williams explained. Co-senior study author Dr. Alan Schatzberg, a professor of psychiatry and behavioral sciences at Stanford explained that the ketamine was not working as “everyone thought it was working.”

Heifets noted that ketamine is a drug of abuse (called “Special K” in party circuits) that has been in use for a long time and there is an abuse potential of this drug acting on the opioid receptors to provide such effects. He warned that this abuse potential should be kept in mind before ketamine comes into the market as an antidepressant.

However the whole team agrees that this new study shows how ketamine can help patients who have intractable depression. New drugs could be developed in the same lines they explain. These drugs could possibly activate the opioid receptors without having abuse potential they add. Williams added that ketamine has been seen to provide relief of symptoms in other mental ailments such as obsessive compulsive disorders and now is the time to explore if opioids play a role in these diseases as well.

Mark George, a professor of psychiatry, radiology and neuroscience at the Medical University of South Carolina in an editorial accompanying the article wrote that this study is a small one and so should be confirmed in larger trials before conclusions could be drawn.

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